Turbine nozzle guide vane construction



Oct. 6, 1953 w BOYD ET AL 2,654,566

TURBINE NOZZLE GUIDE VANE CONSTRUCTION Filed Feb. 11, 1950 2Sheets-Sheet 1 INVENTOR WINNET T BOYD JOSEPH T Pl/HVI-f ATTORNEYPatented Oct. 6, 1953 TURBINE NOZZLE GUIDE VANE CONSTRUCTION WinnettBoyd, Bobcaygeon, Ontario, and Joseph Thompson Purvis, Toronto, Ontario,Canada, assignors to A. V. Roe Canada Limited, Ontario, Ontario, Canada,a corporation Application February 11, 1950, Serial No. 143,724

4 Claims.

This invention relates to turbine and other axial flow power conversionmachines wherein the blading is subjected to a flow of fluid atrelatively high temperatures. The invention more specifically relates toa mounting for turbine nozzle guide vanes.

An object of the invention is to provide a mounting for turbine nozzleguide vanes which provides firm support against the loads imposed by theworking fluid but permits ample relative movement between the bladingand the adjacent structures in response to temperature variations.

Another object of the invention is to provide a mounting that permitseach guide vane to expand or contract independently in relation to theadjoining guide vanes.

Another object of the invention is to provide a system of guide vanemounting wherein the loads imposed by the working fluid tend to hold theguide. vanes firmly against their mountings thereby helping to supportthe guide vanes and minimizing the leakage of working fluid through theinterstice between the base portions of the guide vanes and between thebase portions and adjacent members.

A still further object of the invention is to provide a system of guidevane mounting that permitsthe ready removal and replacement of worn ordamaged parts.

Other objects and advantages will become apparent during the course ofthe following description.

In the drawings accompanying and forming a part of this specification,in which like reference characters are used to designate like partsthroughout the several views,

Fig. 1 is a fragmentary perspective view of a turbine casing structureand turbine nozzle guide vanes constructed according to the invention,as observed when viewed in a direction parallel to the axis of theturbine and in the same sense as the fluid flow;

Fig.2 is a fragmentary sectional view taken on a radial plane throughthe casing structure and viewed in the direction of the arrow 2 in Fig.l; and.

Fig. 3 is a fragmentary perspective view showing one of the turbinenozzle guide vanes in spaced relationship with the vane mounting ring,as observed when viewed in a sense opposite to that of the fluid flow.

Referring to the drawings, a typical turbine comprises a fixed outercasing I and a fixed inner structure II spaced from the said casing andproviding a passage for the flow of fluid from the usual nozzle box (notshown) into the turbine. Suitable means are provided to hold the casingand the inner structure in spaced relationship. (The words inner andouter as used herein refer to the senses radial to the engine and thewords front and rear are used in reference to the direction of the flowof the stream of gases passing through the engine, front denoting theupstream or inlet side and rear denoting the downstream or outlet side.)

According to the invention, a plurality of nozzle guide vanes I2 extendradially across an annular gap I3, located between the fixed innerstructure II and the fixed outer casing II). A circumferential channelI4 is provided in the inner structure I I, the sides of the said channelbeing defined by an annular flange I5 on the inner structure II and aflanged retaining ring I5 attached thereto. At the outer side of theannular gap I3 there is similarly provided a circumferential channel I1lying between the rear face Ill of the outer casing I0 and a turbineshroud ring I8 secured to the outer casing.

Each guide vane has an outer base member or platform I9 and an innerbase member or platform 20, which provide means for mounting the vanesin the channels I I and I4. Since the vanes I2 curve away from the axialdirection at a considerable angle and adjacent vanes must be spacedrelatively closely together, the inner and outer vane platforms 20 and I9 are skewed so that the rear edge of each vane platform is not in axialalignment with the front edge but is displaced tangentially to theturbine in the direction of curvature of the guide vanes (see Fig. 3).

The inner platform 20 has an inwardly project- 'ing mounting dowel 2!that engages in a hole 22' in a vane mounting ring 22 located in thechannel I4. The mounting ring 22 is prevented from rotating with respectto the inner structure II by means of teeth 23 that engage symmetricallyspaced radial slots 24 provided in flange I5 of the inner structure II.The engagement of the teeth 23 in slots 24 alsomaintains theconcentricity of the mounting ring 22 with respect to the innerstructure II regardless of relative expansion or contraction of the ring22 and of the inner structure I I.

The outer platform 19 of each of the guide vanes I2 is located in thechannel I! and has at the rear thereof an outwardly projecting flange25, the outer extremity of which is sufficiently spaced from the innersurface III of the outer casing II) in channel I1 to provide clearancefor the maximum outward expansion of guide vane l2 and mounting ring 22.The clearance thus provided is however, less than the length of dowel 2|on the inner platform 20, for reasons which will subsequently appear.

At the front of the outer platform Hi there is provided an outwardlyprojecting flange 2B which has a slot 21 engaging with one of a seriesof evenly spaced teeth 28 provided on the outer casing ll), wherebytangential displacement of the vane I2 is prevented while permittingradial displacement caused by relative expansion or contraction of thevane and outer casing. As in the case of rear flange 25, the dimensionsof the front flange 26 are arranged to provide suflicient clearance forsuch radial displacement.

A clamping band 29 of relatively thin flat material having suitablestandard means to adjust its tension encircles all of the outerplatforms of the guide vanes and is held in place by ridges 3D and 3|provided on the outer platforms [9. On first assembly of the engine, theband 29 is adjusted so that it fits snugly under light tension. As themachine warms up, the mounting ring 22 and the guide vanes I2 expandoutwardly against the clamping band 29, stretching the latter beyond itsyield point and causing plastic yielding of the band. The tension in theband keeps all the guide vanes in firm contact with the mounting ringand ensures that they remain concentrically disposed about the axis ofthe machine. On cooling down the clamping band 29 i no longer tight, andthe vanes on the under side of the engine are prevented from falling outof place by the rear flange 25 on the outer platform IS; the clearancesare such that the outer tips of the rear flanges will then engage theinner surface l of the outer casing I0, and prevent the dowel 2| frombeing withdrawn from hole 22 in the mounting ring 22.

When the machine is run again and warms to operating temperature, theguide vanes expand until they take up the slack in the clamping band 29and further expansion will result in the vanes on the under side of theengine being restored to their original positions by the outwardexpansion of the blades on the upper side. Thus the entire guide vaneassembly resumes its concentric disposition about the axis of themachine, the r outer platforms'of the blades being mutually supportingagainst radially outward displacement, through the medium of the bandwhich surrounds them all. Although the band acquires a permanent stretchduring the initial operation of the engine, it retains some elasticproperties about its newly acquired length and is still capable ofsupporting the vanes, radially, so that their outer flanges 25 are clearof the outer casin l0, when they have attained their operationaltemperature on successive subsequent occasions.

Small tangential clearances are provided between the platforms [9 and 20of adjacent blades when the machine is cold. The clearances disappearwhen the machine warms up so that a smooth-contoured passage through theannular gap between the inner structure I l and the outer casing ID arepresented to the flow of working fluid.

The loads on the vanes imposed by the working fluid may be resolved intoaxial and tangential components. At the inner end of each vane, both ofthese components are carried by the mounting dowel 2|. At the outer endof each vane, the axial loading is carried by the reaction of theturbine shroud ring 18 against the rear extension 25 of the outerplatform 19. The tangential loading is carried by the tangentialreaction of the tooth 28 against the slot 21.

One of the advantages of the invention may be better understood byconsidering the couples acting on the outer vane platform l9 andresolving these about the point of contact between the tooth 28 and theslot 21, it will be seen that the turning moment induced by theresultant of the gas loads on the vane must be balanced by the moment ofan axial reaction between the turbine shroud ring [8 and the rear flange25 of the outer platform i9. Because of the tangential displacement ofthe rear flange 25 in relation to the front flange 26, the reactionforce against the rear flange 25 that produces the balancing coupletends to be distributed uniformly across the width of the rear flange.

If so desired, thermal insulation material may be placed in the channelsl4 and IT, in order to prevent excessive loss of heat from the guidevanes and also to prevent the damage to other parts that such escapingheat might cause.

It is to be understood that the form of the invention, herewith shownand described, is to be taken as a preferred example of the same, andthat various changes in the shape, size and arrangement of the parts maybe resorted to, without departing from the spirit of the invention orthe scope of the claims.

What we claim as our invention is:

1. In an axial flow elastic fluid power conver sion machine comprising aflxed outer casing structure and a fixed inner structure spaced fromsaid casing structure and defining therewith an annular passage for theflow of fluid, a plurality of guide v-anes extending generally radiallybetween the inner structure and the outer casing structure, and havinginner and outer platforms, a pin and socket connection between each ofthe inner platforms of the guide vanes and the inner structure, the pinbeing radially slidable in the socket, and the blades thereby being freefor radial movement relative to the inner structure, the saidconnections spacing said inner platforms angularly about the axis of themachine, platform-engaging means connecting the outer platforms of theguide vanes to the outer casing structure, said platform-engaging meanspermitting radial expansion and contraction of the guide vanes andrestraining tangential and axial displacement thereof, and an elasticclamping band resiliently encircling all the outer platforms andrendering the platforms mutually supporting against radially outwarddisplacement when the machine is at its operating temperature.

2. In an axial flow elastic fluid power conversion machine comprising afixed outer casing structure and a fixed inner structure spaced fromsaid casing and defining therewith an annular passage for the flow offluid, a plurality of guide vanes extending generally radially betweenthe fixed inner structure and the fixed outer casing structure andhaving inner and outer platforms, a ring member in rotation-preventingengagement with the fixed inner structure, a pin and socket connectionbetween each of the inner platforms of the guide vanes and the innerstructure, the pin being radially slidable in the socket and the bladesthereby being free for radial movement relative to the inner structure,platformengaging means connecting the outer platforms of the guide vanesto the outer casing structure, said platform-engaging means permittingradial expansion and contraction of the guide vanes and preventingtangential and axial displacement thereof, and an elastic clamping bandof relatively thin material resiliently encircling all the said outerplatforms and rendering the platforms mutually supporting againstradially outward displacement when the machine is at its operatingtemperature.

3. In an axial flow elastic fluid power conversion machine comprising afixed outer casing structure and a fixed inner structure with a rimportion having a plurality of radial slots formed therein, said outerand inner structures defining a passage for the flow of fluid, aplurality of guide vanes extending between the fixed inner structure andthe fixed outer casing structure, inner and outer platforms on the guidevanes, a mounting ring having a plurality of holes and having in oneedge a plurality of teeth in engagement with the radial slots in thefixed inner structure, dowels secured to the inner platforms of theguide vanes and extending into the holes in the ring member, said ringmember engaging the inner platforms to limit radially inwarddisplacement of the guide vanes the fixed outer casing having a channelin which the outer platforms of the guide vanes are secured axially,teeth in the side of the channel, and means in the outer platform forengaging the teeth and securing the outer platforms tangentially, and aclamping band encircling all the outer platform and rendering theplatforms mutually supporting against radially outward displacement whenthe machine is at its operating temperature.

4. In an axial flow elastic fluid power conversion machine comprising afixed outer casing structure and a fixed inner structure with a rimstructure having a plurality of radial slots formed therein, said outerand inner structures defining a passage for the fiow of fluid from thefront to the rear of the passage, a plurality of guide vanes extendingbetween the fixed inner structure and the fixed outer casing structure,inner and outer platforms on the guide vanes, a front flange and a rearflange on each of the outer platforms, the front flanges having notchestherein, a mounting ring having a plurality of holes and having in oneedge a plurality of teeth in engagement with the radial slots in thefixed inner structure, dowels secured to the inner platform of the guidevanes and extending into the holes in the ring member, said ring memberengaging the inner platforms to limit radially inward dsplacement of theguide vanes the fixed outer casing having a channel into which the frontflanges and rear flanges on the outer platforms extend, teeth in theside of the channel engaging the notches in the front flanges, and aclamping band encircling all the outer platforms and rendering theplatforms mutually supporting against radially outward displacement whenthe machine is at its operating temperature.

WINNETT BOYD. JOSEPH THOMPSON PURVIS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,061,675 Junggren May 13, 1913 2,447,942 Imbert Aug. 24, 19482,488,875 Morley Nov. 22, 1949 2,494,821 Lombard Jan. 17, 1950 FOREIGNPATENTS Number Country Date 216,7 7 Great Britain June 5, 1924 611,326Great Britain Oct. 28, 1948

